1. Field of the Invention
The present invention relates to an optical element, and more specifically, it relates to an optical element that has a part with a fine textured structure where incident rays are totally reflected.
2. Description of the Related Art
Optical elements (lenses) having various shapes and refractive indices are used in optical systems used for photography.
In particular, a concave meniscus lens or the like used as the front (object-side) lens of a wide-angle lens has a part where some of incident rays other than photographing light are totally reflected. The totally reflected rays are reflected again by the edge of the lens or a component of the lens barrel and reach the image plane. This generates unwanted light defects in a photograph such as flare or ghost images.
To prevent flare or ghost images, an antireflection film that is a dielectric multilayer film (also called multicoat film) formed on the surface of lenses has been proposed. Notwithstanding the high-performance of an antireflection film, such a film cannot prevent total reflection, and therefore it cannot solve the above-described problem.
Another solution to the above-described problem has been by Japanese Patent Laid-Open No. 10-307256 (hereafter “JP 10-307256”). JP 10-307256 discloses a configuration in which a second lens having negative refractive power is cemented to a first lens having positive refractive power to prevent total reflection on the second surface of the first lens.
In the disclosure of JP 10-307256, two lenses having opposite signs of refractive power are cemented together. Such a cemented lens having a desired refractive power is large, heavy, and expensive to manufacture.